Method of making a display device



1968 T. v. RYCHLEWSKI 3,

METHOD OF MAKING A DISPLAY DEVICE Filed May 27, 1964 2 Sheets-Sheet 1 INVENTOR 794005115 V. RYCHLEWSKI ATTORNEY Feb. 27, 1968 T. v. RYCHLEWSKI 3,370,976

7 METHOD 0F MAKING A DISPLAY DEVICE Filed May 27, 1964 2 Sheets-Sheet 2 l NVENTOR 7702005115 14 KYc/mms/w ATTORJN EY United States Patent 3,370,976 METHQD OF MAKING A DESPLAY DEVICE Thaddeus V. Rychlewslri, Seneca Falls. N.Y., assignor to Sylvania Electric Products Inc a corporaticn of Delaware Filed May 27, 1964, Ser. No. 370,655 6 Claims. (Cl. 117-212) ABSTRACT OF THE DISCLOSURE A numeric readout device and a process of making the same which utilizes the edge illumination of excited electroluminescent material. The device is fabricated by applying the electrodes and EL material to the periphery of a substrate rather than to the planar surface thereof. This procedure allows the use of thin line figures while maintaining large electrical contact areas for ease of electrical connection.

This invention generally relates to display devices and to a method of making the same. More particularly, it relates to illuminable symbolic and numeric readout displays and a method of making them.

The tremendous increase in the number of electronic computing and testing devices has created a need for visible display units which may be utilized in visually portraying the information derived therefrom. There have been many types of these units, all of which have been more or less successful. These include mechanical counters, gas glow tubes, projection devices, and segmented electroluminescent displays. This invention pertains to the latter type of device.

The usual type of segmented electroluminescent display is comprised of an electrically insulating planar substrate having a particular, electrically conductive, segmented pattern afiixed thereto. Overlying this pattern is a layer of an electroluminescent phosphor which may or may not be dispersed in a dielectric medium such as plastic or glass frit. A common transparent, electrically conductive electrode overlies the electroluminescent layer. When a potential is applied between the common transparent electrode and any one or several of the conductive segments, the electroluminescent phosphor therebetween will be excited to luminescence. These devices are quite superior to many of the types in common usage today in that they are not subject to catastrophic failure. They have, however, several disadvantages. Among these are the problems of constructing small displays and the dimculty of providing electrical connection to the various segments.

It is, therefore, an object of this invention to provide a small symbolic readout display having improved manufacturability.

It is another object of this invention to provide an improved electroluminescent readout device.

Another object of this invention is to provide im proved means for making electrical connections to readout devices.

Still another object of the invention is to provide a readout device having an improved structure adapted to the economic fabrication thereof.

The above objects are carried out in one aspect of the invention by the provision of a method of making illuminable symbolic readout displays which comprises coating the peripheral surface area of a rod having a given geometrical configuration, and at least the peripheral surface of which is electrically conducting, with an electroluminescent phosphor. Next, an electrically conductive coating is applied over the phosphor, and then discrete areas 3,370,976 Patented Feb. 27, 1968 of the conductive coating are removed whereby a pluraiity of individually illuminable electroluminescent segments is provided.

It will be seen that, by the use of this method, relatively small and rugged electroluminescent symbolic displays may be fabricated since the size will be controlled by the dimensions of the rod. By making the rod longer than the phosphor layer, electrical connection may be easily accomplished to the inner electrode. By forming several symbolic displays and assembling them together, numeric segmented displays may be provided.

For a better understanding of the present invention, together with other and further objects, advantages, and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the accompanying drawings in which:

FIGURES 1 through 5 illustrate the sequence of operations for fabricating one type of symbolic display device;

FIGURES 6 through 9 illustrate the sequence of operations for fabricating another type of symbolic display device; and

FIGURE 10 is an exploded perspective view illustrating a type of numeric readout display which may be assembled from the two symbolic display devices.

Referring now to the drawings with greater particularity, in FIGURE 1 there is shown a rod 12 of some suitable opaque material such as glass orceramic or electrically conductive metal. If rod 12 is metal, the elec troluminescent phosphor may be applied directly thereto; however, if the rod is glass or ceramic. or some other electrically insulating material, then an electrically conductive coating such as 14 in FIGURE 2 would have to be applied thereto to provide an inner electrode. Coating 14 may be any suitable and easily applied material such as aluminum or gold.

Phosphor layer 16 is then applied to coating 14 by any conventional means, as by spraying, and may consist of all phosphor or phosphor particles dispersed in a dielectric medium such as glass frit or plastic. Layer 16 does not extend the entire length of rod 12 so that electrical connection can be made to coating 14.

Conductive coating 18 may be applied over layer 16 by suitable means to provide the construction shown in FIGURE 4; and then selected, discrete areas of coating 18 are removed to form a plurality of individual outer electrodes 20, 22, 24, 26 which provide individually illuminable electroluminescent segments in a first symbolic display device 28. While rod 12 is shown in this instance as having a substantially parallelogrammatic configuration, it is to be understood that other polygonal configurations may be used for other purposes with equal Success. For example, if rod 12 has a decagonal configuration, a ten-segrncnt decade counter could be produced.

Symbolic display devices constructed according to the method of this invention provide a distinct advance in the art. Small, rugged units of virtually any configuration can be constructed, and electrical connection to the various electrodes can be easily accomplished.

To construct a numeric readout display; that is, a display which portrays the conventional physical characteristics of numbers, the following approach has been tried:

An electrically insulating rod 30, similar in size and configuration to rod 12, has first and second electrically conductive coatings, 32, 34 respectively, applied thereto as is shown in FIGURE 6. Coating 32 extends the full length of rod 30 and encompasses substantially three surfaces thereof. Coating 34 is adhered to the previously uncoated surface and is insulated from coating 32 and also extends the full length of rod 30.

Phosphor layer 36 is applied by suitable means to overlie coating 32, and a third electrically conductive coating 38 is applied thereover. Again, layer 36 and coating 38 preferably do not extend the full length of rod 30. Selected, discrete areas of coating 38 are then removed, as by grinding, to form a plurality of electrodes 4%, 42, 44 which provide individually illuminable electroluminescent segments in a second symbolic display device 46.

While it has been suggested to apply coating 18 and coating 38 in a more or less enveloping manner and then remove selected, discrete areas thereof to form electrodes, it will be obvious to those skilled in the art that the electrodes could be individually applied.

Numeric readout display 48 is formed by combining a first symbolic display device 28 and a second symbolic display device 46 in the stacked manner shown in FIG- URE 10. Preferably they may be cemented together by a conductive epoxy. This unit is then affixed in connector board 50 by any suitable means, such as by cementing. Board 50 may be any electrically insulating material having good strength characteristics; and it is provided with connector pins 52, 54, 56, 53, 60, 62, 64, 66 which provide electrical contact with electrodes 40, 32, 34, 42, 14, 22, 24, 26, and 44 respectively. The connector pins project through board 50 so that the entire unit may be connected to suitable electrical potentials.

This device is small and rugged and is relatively economical to manufacture, and it greatly simplifies the job of making electrical connection to the various segments.

While there have been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention as defined by the appended claims.

What is claimed is:

1. A method of making illuminable symbolic displays utilizing the edge illumination of an electroluminescent phosphor comprising the steps of: coating the peripheral surface area of an electrically insulating rod having a given geometrical configuration with an electrically conductive material; applying an electroluminescent phosphor over said coating; applying a second electrically conductive coating over said phosphor; and removing discrete areas of said second coating whereby a plurality of individually illuminable electroluminescent segments is provided.

2. A method of making illuminable symbolic displays utilizing the edge illumination of an electroluminescent phosphor comprising the steps of: coating the peripheral surface area of an electrically insulating rod having a given geometrical configuration with an electrically conductive material for a given distance along said rod, applying an electroluminescent phosphor over said coating for a distance less than said given distance; applying a second electrically conductive coating over said phosphor; and removing discrete areas of said second coating whereby a plurality of individually illuminable electroluminescent segments is provided.

3. A method of making illuminable displays utilizing the edge illumination of an electroluminescent phosphor comprising the steps of: coating the peripheral surface area of a rod, at least the peripheral surface of which is capable of conducting electricity, with an electroluminescent phosphor; applying an electrically conductive coating over said phosphor; and removing discrete areas of said coating whereby a plurality of individually illuminable electroluminescent segments is provided.

4. A method of making illuminable numeric readout displays utilizing the edge illumination of an electroluminescent phosphor comprising the steps of: forming a first portion of said display by coating the peripheral surface area of an opaque, electrically insulating rod having a substantially parallelogrammatic cross-section with an electrically conductive material; applying an electroluminescent phosphor over said coating; applying a second coating of electrically conductive material over said phosphor; removing discrete areas of said second coating whereby a plurality of individually illuminable segments is provided; and forming a second portion of said display by coating three of the peripheral surface areas of an opaque, electrically insulating rod having a substantially parallelogrammatic cross-section with a first coating of an electrically conductive material; applying a second electrically conductive material to the previously uncoated surface of said rod, said first coating and said second coating being insulated from one another; applying an electroluminescent phosphor over said first coating; applying a third electrically conductive coating over said phosphor; removing discrete areas of said third coating whereby a plurality of individually illuminable segments is formed; and positioning said second portion and said first portion together to form a numeric display.

5. A method of making illuminable symbolic displays utilizing the edge illumination of an electroluminescent phosphor comprising the steps of: coating the peripheral surface area of an opaque rod, at least the peripheral surface of which is electrically conductive, with an electroluminescent phosphor, applying an electrically conductive coating over said phosphor; and removing discrete areas of said coating whereby a plurality of individually illuminable segments is provided.

6. A method of making illuminable symbolic displays utilizing the edge illumination of an electroluminescent phosphor comprising the steps of: coating the peripheral surface area of an opaque rod, at least the peripheral surface of which is electrically conductive, with an electroluminescent phosphor; and forming a plurality of electrodes on said phosphor whereby individually illuminable segments are provided.

References Cited UNITED STATES PATENTS 3/1954 Sukacev 29-1555 11/1966 Bullinger 313-l08 WILLIAM L. JARVIS, Primary Examiner, 

